Process for refining petroleum fractions

Claim 1

A PROCESS FOR UPGRADING THE MID-BOILING FRACTIONS OF PETROLEUM CRUDE OIL WHICH COMPRISES FLASHING A TOPPED CRUDE OIL UNDER VACUM AT A FLASH TEMPERATURE ABOVE ABOUT 900*F. (EVUIVALENT AT 760 MM. HG) TO PRODUCE A HEAVY GAS OIL FRACTION HAVING A BOILING RANGE OF ABOUT 500 TO 1050*F., CATALYTICALLY CRACKING SAID HEAVY GAS OIL FRACTION IN ONE-PASS CATALYTIC CRACKING ZONE AT A TEMPERATURE BETWEEN 750 AND 1050*F., DISTILLING THE CATALYTICALLY CRACKED PRODUCT TO SEPARATE FURNACE OIL AND LIGHTER FRACTIONS AND A HEAVY RESIDENTIAL FRACTINAND PRODUCE A CYCLE OIL FRACTION BOILING WITHIN THE RANGE OF ABOUT 400* TO 750* F., PASSING SAID CYCLE OIL TO A STEAM CRACKER, STEAM CRACK ING SAID CYCLE OIL AT A LOW PRESSURE AND AT A TEMPERATURE BETWEEN 1100 AND 1500*F. AND A HOLDING TIME OF 0.1 TO 2.5 SECONDS, DISTILLING THE STEAM CRACKED PRODUCT TO SEPARATE HYDROCARBONS BOILING AT ABOUT 450*F. OR LESS AND TO PRODUCE A SIDE STREAM FRACTION BOILING BETWEEN 450 AND 650*F. AND A TAR BOTTOMS FRACTION BOILING ABOVE ABOUT 650*F. AND UP TO ABOUT 1200*F., CONTACTING SAID SIDE STREAM FRACTION WITH HYDROGEN IN AT LEAST ONE HYDROCRACKING STAGE IN THE PRESENCE OF A HYDROCRACKING CATALYST AT A TEMPERATURE BETWEEN 550 AND 800*F. AND DISTILLING THE RESULTING HYDROCRACKED PRODUCT TO SEPARATE A RESIDUE FRACTION FROM A PRODUCT GASOLINE FRACTION, PASSING SAID TAR BOTTOMS FRACTION RESULTING FROM THE DISTILLATION OF SAID STEAM-CRACKED PRODUCT INTO A THERMAL SOAKING ZONE, SUBJECTING SAID TAR BOTTOMS FRACTION TO A TEMPERATURE BETWEEN 750 AND 950*F. FOR A PERIOD OF FROM 2 TO 6 HOURS TO CONVERT SAID TAR BOTTOMS TO PITCH AND MORE VOLATILE PRODUCTS, PASSING SAID PITCH AND VOLATILE PRODUCTS TO A DISTILLATION ZONE AND THERIEN STRIPPING THE PITCH OF SUBSTANTIALLY ALL THE VIOLATE PRODUCTS BOILING BELOW ABOUTG 750*F.